/******************************************************
Database log

(c) 1995-1997 Innobase Oy

Created 12/9/1995 Heikki Tuuri
*******************************************************/

#include "log0log.h"

#ifdef UNIV_NONINL
#include "log0log.ic"
#endif

#include "mem0mem.h"
#include "buf0buf.h"
#include "buf0flu.h"
#include "srv0srv.h"
#include "log0recv.h"
#include "fil0fil.h"
#include "dict0boot.h"
#include "srv0srv.h"
#include "srv0start.h"
#include "trx0sys.h"
#include "trx0trx.h"

/*
General philosophy of InnoDB redo-logs:

1) Every change to a contents of a data page must be done
through mtr, which in mtr_commit() writes log records
to the InnoDB redo log.

2) Normally these changes are performed using a mlog_write_ulint()
or similar function.

3) In some page level operations only a code number of a
c-function and its parameters are written to the log to
reduce the size of the log.

  3a) You should not add parameters to these kind of functions
  (e.g. trx_undo_header_create(), trx_undo_insert_header_reuse())

  3b) You should not add such functionality which either change
  working when compared with the old or are dependent on data
  outside of the page. These kind of functions should implement
  self-contained page transformation and it should be unchanged
  if you don't have very essential reasons to change log
  semantics or format.

*/

/* Current free limit of space 0; protected by the log sys mutex; 0 means
uninitialized */
ulint log_fsp_current_free_limit = 0;

/* Global log system variable */
log_t *log_sys = NULL;

#ifdef UNIV_DEBUG
ibool log_do_write = TRUE;

ibool log_debug_writes = FALSE;
#endif /* UNIV_DEBUG */

/* These control how often we print warnings if the last checkpoint is too
old */
ibool log_has_printed_chkp_warning = FALSE;
time_t log_last_warning_time;

#ifdef UNIV_LOG_ARCHIVE
/* Pointer to this variable is used as the i/o-message when we do i/o to an
archive */
byte log_archive_io;
#endif /* UNIV_LOG_ARCHIVE */

/* A margin for free space in the log buffer before a log entry is catenated */
#define LOG_BUF_WRITE_MARGIN (4 * OS_FILE_LOG_BLOCK_SIZE)

/* Margins for free space in the log buffer after a log entry is catenated */
#define LOG_BUF_FLUSH_RATIO 2
#define LOG_BUF_FLUSH_MARGIN (LOG_BUF_WRITE_MARGIN + 4 * UNIV_PAGE_SIZE)

/* Margin for the free space in the smallest log group, before a new query
step which modifies the database, is started */

#define LOG_CHECKPOINT_FREE_PER_THREAD (4 * UNIV_PAGE_SIZE)
#define LOG_CHECKPOINT_EXTRA_FREE (8 * UNIV_PAGE_SIZE)

/* This parameter controls asynchronous making of a new checkpoint; the value
should be bigger than LOG_POOL_PREFLUSH_RATIO_SYNC */

#define LOG_POOL_CHECKPOINT_RATIO_ASYNC 32

/* This parameter controls synchronous preflushing of modified buffer pages */
#define LOG_POOL_PREFLUSH_RATIO_SYNC 16

/* The same ratio for asynchronous preflushing; this value should be less than
the previous */
#define LOG_POOL_PREFLUSH_RATIO_ASYNC 8

/* Extra margin, in addition to one log file, used in archiving */
#define LOG_ARCHIVE_EXTRA_MARGIN (4 * UNIV_PAGE_SIZE)

/* This parameter controls asynchronous writing to the archive */
#define LOG_ARCHIVE_RATIO_ASYNC 16

/* Codes used in unlocking flush latches */
#define LOG_UNLOCK_NONE_FLUSHED_LOCK 1
#define LOG_UNLOCK_FLUSH_LOCK 2

/* States of an archiving operation */
#define LOG_ARCHIVE_READ 1
#define LOG_ARCHIVE_WRITE 2

/**********************************************************
Completes a checkpoint write i/o to a log file. */
static void log_io_complete_checkpoint(void);
/*============================*/
#ifdef UNIV_LOG_ARCHIVE
/**********************************************************
Completes an archiving i/o. */
static void log_io_complete_archive(void);
/*=========================*/
#endif /* UNIV_LOG_ARCHIVE */

/********************************************************************
Sets the global variable log_fsp_current_free_limit. Also makes a checkpoint,
so that we know that the limit has been written to a log checkpoint field
on disk. */

void log_fsp_current_free_limit_set_and_checkpoint(
    /*==========================================*/
    ulint limit) /* in: limit to set */
{
  ibool success;

  mutex_enter(&(log_sys->mutex));

  log_fsp_current_free_limit = limit;

  mutex_exit(&(log_sys->mutex));

  /* Try to make a synchronous checkpoint */

  success = FALSE;

  while (!success)
  {
    success = log_checkpoint(TRUE, TRUE);
  }
}

/********************************************************************
Returns the oldest modified block lsn in the pool, or log_sys->lsn if none
exists. */
static dulint log_buf_pool_get_oldest_modification(void)
/*======================================*/
{
  dulint lsn;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  lsn = buf_pool_get_oldest_modification();

  if (ut_dulint_is_zero(lsn))
  {
    lsn = log_sys->lsn;
  }

  return (lsn);
}

/****************************************************************
Opens the log for log_write_low. The log must be closed with log_close and
released with log_release. */

dulint log_reserve_and_open(
    /*=================*/
    /* out: start lsn of the log record */
    ulint len) /* in: length of data to be catenated */
{
  log_t *log = log_sys;
  ulint len_upper_limit;
#ifdef UNIV_LOG_ARCHIVE
  ulint archived_lsn_age;
  ulint dummy;
#endif /* UNIV_LOG_ARCHIVE */
#ifdef UNIV_DEBUG
  ulint count = 0;
#endif /* UNIV_DEBUG */

  ut_a(len < log->buf_size / 2);
loop:
  mutex_enter(&(log->mutex));

  /* Calculate an upper limit for the space the string may take in the
  log buffer */

  len_upper_limit = LOG_BUF_WRITE_MARGIN + (5 * len) / 4;

  if (log->buf_free + len_upper_limit > log->buf_size)
  {
    mutex_exit(&(log->mutex));

    /* Not enough free space, do a syncronous flush of the log
    buffer */

    log_buffer_flush_to_disk();

    srv_log_waits++;

    ut_ad(++count < 50);

    goto loop;
  }

#ifdef UNIV_LOG_ARCHIVE
  if (log->archiving_state != LOG_ARCH_OFF)
  {
    archived_lsn_age = ut_dulint_minus(log->lsn, log->archived_lsn);
    if (archived_lsn_age + len_upper_limit > log->max_archived_lsn_age)
    {
      /* Not enough free archived space in log groups: do a
      synchronous archive write batch: */

      mutex_exit(&(log->mutex));

      ut_ad(len_upper_limit <= log->max_archived_lsn_age);

      log_archive_do(TRUE, &dummy);

      ut_ad(++count < 50);

      goto loop;
    }
  }
#endif /* UNIV_LOG_ARCHIVE */

#ifdef UNIV_LOG_DEBUG
  log->old_buf_free = log->buf_free;
  log->old_lsn = log->lsn;
#endif
  return (log->lsn);
}

/****************************************************************
Writes to the log the string given. It is assumed that the caller holds the
log mutex. */

void log_write_low(
    /*==========*/
    byte *str,     /* in: string */
    ulint str_len) /* in: string length */
{
  log_t *log = log_sys;
  ulint len;
  ulint data_len;
  byte *log_block;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log->mutex)));
#endif /* UNIV_SYNC_DEBUG */
part_loop:
  /* Calculate a part length */

  data_len = (log->buf_free % OS_FILE_LOG_BLOCK_SIZE) + str_len;

  if (data_len <= OS_FILE_LOG_BLOCK_SIZE - LOG_BLOCK_TRL_SIZE)
  {
    /* The string fits within the current log block */

    len = str_len;
  }
  else
  {
    data_len = OS_FILE_LOG_BLOCK_SIZE - LOG_BLOCK_TRL_SIZE;

    len = OS_FILE_LOG_BLOCK_SIZE - (log->buf_free % OS_FILE_LOG_BLOCK_SIZE) - LOG_BLOCK_TRL_SIZE;
  }

  ut_memcpy(log->buf + log->buf_free, str, len);

  str_len -= len;
  str = str + len;

  log_block = ut_align_down(log->buf + log->buf_free, OS_FILE_LOG_BLOCK_SIZE);
  log_block_set_data_len(log_block, data_len);

  if (data_len == OS_FILE_LOG_BLOCK_SIZE - LOG_BLOCK_TRL_SIZE)
  {
    /* This block became full */
    log_block_set_data_len(log_block, OS_FILE_LOG_BLOCK_SIZE);
    log_block_set_checkpoint_no(log_block, log_sys->next_checkpoint_no);
    len += LOG_BLOCK_HDR_SIZE + LOG_BLOCK_TRL_SIZE;

    log->lsn = ut_dulint_add(log->lsn, len);

    /* Initialize the next block header */
    log_block_init(log_block + OS_FILE_LOG_BLOCK_SIZE, log->lsn);
  }
  else
  {
    log->lsn = ut_dulint_add(log->lsn, len);
  }

  log->buf_free += len;

  ut_ad(log->buf_free <= log->buf_size);

  if (str_len > 0)
  {
    goto part_loop;
  }

  srv_log_write_requests++;
}

/****************************************************************
Closes the log. */

dulint log_close(void)
/*===========*/
/* out: lsn */
{
  byte *log_block;
  ulint first_rec_group;
  dulint oldest_lsn;
  dulint lsn;
  log_t *log = log_sys;
  ulint checkpoint_age;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  lsn = log->lsn;

  log_block = ut_align_down(log->buf + log->buf_free, OS_FILE_LOG_BLOCK_SIZE);
  first_rec_group = log_block_get_first_rec_group(log_block);

  if (first_rec_group == 0)
  {
    /* We initialized a new log block which was not written
    full by the current mtr: the next mtr log record group
    will start within this block at the offset data_len */

    log_block_set_first_rec_group(log_block, log_block_get_data_len(log_block));
  }

  if (log->buf_free > log->max_buf_free)
  {
    log->check_flush_or_checkpoint = TRUE;
  }

  checkpoint_age = ut_dulint_minus(lsn, log->last_checkpoint_lsn);

  if (checkpoint_age >= log->log_group_capacity)
  {
    /* TODO: split btr_store_big_rec_extern_fields() into small
    steps so that we can release all latches in the middle, and
    call log_free_check() to ensure we never write over log written
    after the latest checkpoint. In principle, we should split all
    big_rec operations, but other operations are smaller. */

    if (!log_has_printed_chkp_warning || difftime(time(NULL), log_last_warning_time) > 15)
    {
      log_has_printed_chkp_warning = TRUE;
      log_last_warning_time = time(NULL);

      ut_print_timestamp(stderr);
      fprintf(stderr,
              "  InnoDB: ERROR: the age of the last checkpoint is %lu,\n"
              "InnoDB: which exceeds the log group capacity %lu.\n"
              "InnoDB: If you are using big BLOB or TEXT rows, you must set the\n"
              "InnoDB: combined size of log files at least 10 times bigger than the\n"
              "InnoDB: largest such row.\n",
              (ulong)checkpoint_age, (ulong)log->log_group_capacity);
    }
  }

  if (checkpoint_age <= log->max_modified_age_async)
  {
    goto function_exit;
  }

  oldest_lsn = buf_pool_get_oldest_modification();

  if (ut_dulint_is_zero(oldest_lsn) || (ut_dulint_minus(lsn, oldest_lsn) > log->max_modified_age_async) ||
      checkpoint_age > log->max_checkpoint_age_async)
  {
    log->check_flush_or_checkpoint = TRUE;
  }
function_exit:

#ifdef UNIV_LOG_DEBUG
  log_check_log_recs(log->buf + log->old_buf_free, log->buf_free - log->old_buf_free, log->old_lsn);
#endif

  return (lsn);
}

#ifdef UNIV_LOG_ARCHIVE
/**********************************************************
Pads the current log block full with dummy log records. Used in producing
consistent archived log files. */
static void log_pad_current_log_block(void)
/*===========================*/
{
  byte b = MLOG_DUMMY_RECORD;
  ulint pad_length;
  ulint i;
  dulint lsn;

  /* We retrieve lsn only because otherwise gcc crashed on HP-UX */
  lsn = log_reserve_and_open(OS_FILE_LOG_BLOCK_SIZE);

  pad_length = OS_FILE_LOG_BLOCK_SIZE - (log_sys->buf_free % OS_FILE_LOG_BLOCK_SIZE) - LOG_BLOCK_TRL_SIZE;

  for (i = 0; i < pad_length; i++)
  {
    log_write_low(&b, 1);
  }

  lsn = log_sys->lsn;

  log_close();
  log_release();

  ut_a((ut_dulint_get_low(lsn) % OS_FILE_LOG_BLOCK_SIZE) == LOG_BLOCK_HDR_SIZE);
}
#endif /* UNIV_LOG_ARCHIVE */

/**********************************************************
Calculates the data capacity of a log group, when the log file headers are not
included. */

ulint log_group_get_capacity(
    /*===================*/
    /* out: capacity in bytes */
    log_group_t *group) /* in: log group */
{
#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  return ((group->file_size - LOG_FILE_HDR_SIZE) * group->n_files);
}

/**********************************************************
Calculates the offset within a log group, when the log file headers are not
included. */
UNIV_INLINE
ulint log_group_calc_size_offset(
    /*=======================*/
    /* out: size offset (<= offset) */
    ulint offset,       /* in: real offset within the log group */
    log_group_t *group) /* in: log group */
{
#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  return (offset - LOG_FILE_HDR_SIZE * (1 + offset / group->file_size));
}

/**********************************************************
Calculates the offset within a log group, when the log file headers are
included. */
UNIV_INLINE
ulint log_group_calc_real_offset(
    /*=======================*/
    /* out: real offset (>= offset) */
    ulint offset,       /* in: size offset within the log group */
    log_group_t *group) /* in: log group */
{
#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  return (offset + LOG_FILE_HDR_SIZE * (1 + offset / (group->file_size - LOG_FILE_HDR_SIZE)));
}

/**********************************************************
Calculates the offset of an lsn within a log group. */
static ulint log_group_calc_lsn_offset(
    /*======================*/
    /* out: offset within the log group */
    dulint lsn,         /* in: lsn, must be within 4 GB of
                        group->lsn */
    log_group_t *group) /* in: log group */
{
  dulint gr_lsn;
  ib_longlong gr_lsn_size_offset;
  ib_longlong difference;
  ib_longlong group_size;
  ib_longlong offset;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  /* If total log file size is > 2 GB we can easily get overflows
  with 32-bit integers. Use 64-bit integers instead. */

  gr_lsn = group->lsn;

  gr_lsn_size_offset = (ib_longlong)log_group_calc_size_offset(group->lsn_offset, group);

  group_size = (ib_longlong)log_group_get_capacity(group);

  if (ut_dulint_cmp(lsn, gr_lsn) >= 0)
  {
    difference = (ib_longlong)ut_dulint_minus(lsn, gr_lsn);
  }
  else
  {
    difference = (ib_longlong)ut_dulint_minus(gr_lsn, lsn);

    difference = difference % group_size;

    difference = group_size - difference;
  }

  offset = (gr_lsn_size_offset + difference) % group_size;

  ut_a(offset < (((ib_longlong)1) << 32)); /* offset must be < 4 GB */

  /* fprintf(stderr,
          "Offset is %lu gr_lsn_offset is %lu difference is %lu\n",
         (ulint)offset,(ulint)gr_lsn_size_offset, (ulint)difference);
  */

  return (log_group_calc_real_offset((ulint)offset, group));
}

/***********************************************************************
Calculates where in log files we find a specified lsn. */

ulint log_calc_where_lsn_is(
    /*==================*/
    /* out: log file number */
    ib_longlong *log_file_offset, /* out: offset in that file
                                  (including the header) */
    dulint first_header_lsn,      /* in: first log file start
                                  lsn */
    dulint lsn,                   /* in: lsn whose position to
                                  determine */
    ulint n_log_files,            /* in: total number of log
                                  files */
    ib_longlong log_file_size)    /* in: log file size
                                  (including the header) */
{
  ib_longlong ib_lsn;
  ib_longlong ib_first_header_lsn;
  ib_longlong capacity = log_file_size - LOG_FILE_HDR_SIZE;
  ulint file_no;
  ib_longlong add_this_many;

  ib_lsn = ut_conv_dulint_to_longlong(lsn);
  ib_first_header_lsn = ut_conv_dulint_to_longlong(first_header_lsn);

  if (ib_lsn < ib_first_header_lsn)
  {
    add_this_many = 1 + (ib_first_header_lsn - ib_lsn) / (capacity * (ib_longlong)n_log_files);
    ib_lsn += add_this_many * capacity * (ib_longlong)n_log_files;
  }

  ut_a(ib_lsn >= ib_first_header_lsn);

  file_no = ((ulint)((ib_lsn - ib_first_header_lsn) / capacity)) % n_log_files;
  *log_file_offset = (ib_lsn - ib_first_header_lsn) % capacity;

  *log_file_offset = *log_file_offset + LOG_FILE_HDR_SIZE;

  return (file_no);
}

/************************************************************
Sets the field values in group to correspond to a given lsn. For this function
to work, the values must already be correctly initialized to correspond to
some lsn, for instance, a checkpoint lsn. */

void log_group_set_fields(
    /*=================*/
    log_group_t *group, /* in: group */
    dulint lsn)         /* in: lsn for which the values should be
                        set */
{
  group->lsn_offset = log_group_calc_lsn_offset(lsn, group);
  group->lsn = lsn;
}

/*********************************************************************
Calculates the recommended highest values for lsn - last_checkpoint_lsn,
lsn - buf_get_oldest_modification(), and lsn - max_archive_lsn_age. */
static ibool log_calc_max_ages(void)
/*===================*/
/* out: error value FALSE if the smallest log group is
too small to accommodate the number of OS threads in
the database server */
{
  log_group_t *group;
  ulint margin;
  ulint free;
  ibool success = TRUE;
  ulint smallest_capacity;
  ulint archive_margin;
  ulint smallest_archive_margin;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(!mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  mutex_enter(&(log_sys->mutex));

  group = UT_LIST_GET_FIRST(log_sys->log_groups);

  ut_ad(group);

  smallest_capacity = ULINT_MAX;
  smallest_archive_margin = ULINT_MAX;

  while (group)
  {
    if (log_group_get_capacity(group) < smallest_capacity)
    {
      smallest_capacity = log_group_get_capacity(group);
    }

    archive_margin = log_group_get_capacity(group) - (group->file_size - LOG_FILE_HDR_SIZE) - LOG_ARCHIVE_EXTRA_MARGIN;

    if (archive_margin < smallest_archive_margin)
    {
      smallest_archive_margin = archive_margin;
    }

    group = UT_LIST_GET_NEXT(log_groups, group);
  }

  /* Add extra safety */
  smallest_capacity = smallest_capacity - smallest_capacity / 10;

  /* For each OS thread we must reserve so much free space in the
  smallest log group that it can accommodate the log entries produced
  by single query steps: running out of free log space is a serious
  system error which requires rebooting the database. */

  free = LOG_CHECKPOINT_FREE_PER_THREAD * (10 + srv_thread_concurrency) + LOG_CHECKPOINT_EXTRA_FREE;
  if (free >= smallest_capacity / 2)
  {
    success = FALSE;

    goto failure;
  }
  else
  {
    margin = smallest_capacity - free;
  }

  margin = ut_min(margin, log_sys->adm_checkpoint_interval);

  margin = margin - margin / 10; /* Add still some extra safety */

  log_sys->log_group_capacity = smallest_capacity;

  log_sys->max_modified_age_async = margin - margin / LOG_POOL_PREFLUSH_RATIO_ASYNC;
  log_sys->max_modified_age_sync = margin - margin / LOG_POOL_PREFLUSH_RATIO_SYNC;

  log_sys->max_checkpoint_age_async = margin - margin / LOG_POOL_CHECKPOINT_RATIO_ASYNC;
  log_sys->max_checkpoint_age = margin;

#ifdef UNIV_LOG_ARCHIVE
  log_sys->max_archived_lsn_age = smallest_archive_margin;

  log_sys->max_archived_lsn_age_async = smallest_archive_margin - smallest_archive_margin / LOG_ARCHIVE_RATIO_ASYNC;
#endif /* UNIV_LOG_ARCHIVE */
failure:
  mutex_exit(&(log_sys->mutex));

  if (!success)
  {
    fprintf(stderr,
            "InnoDB: Error: ib_logfiles are too small for innodb_thread_concurrency %lu.\n"
            "InnoDB: The combined size of ib_logfiles should be bigger than\n"
            "InnoDB: 200 kB * innodb_thread_concurrency.\n"
            "InnoDB: To get mysqld to start up, set innodb_thread_concurrency in my.cnf\n"
            "InnoDB: to a lower value, for example, to 8. After an ERROR-FREE shutdown\n"
            "InnoDB: of mysqld you can adjust the size of ib_logfiles, as explained in\n"
            "InnoDB: http://dev.mysql.com/doc/mysql/en/Adding_and_removing.html\n"
            "InnoDB: Cannot continue operation. Calling exit(1).\n",
            (ulong)srv_thread_concurrency);

    exit(1);
  }

  return (success);
}

/**********************************************************
Initializes the log. */

void log_init(void)
/*==========*/
{
  byte *buf;

  log_sys = mem_alloc(sizeof(log_t));

  mutex_create(&(log_sys->mutex));
  mutex_set_level(&(log_sys->mutex), SYNC_LOG);

  mutex_enter(&(log_sys->mutex));

  /* Start the lsn from one log block from zero: this way every
  log record has a start lsn != zero, a fact which we will use */

  log_sys->lsn = LOG_START_LSN;

  ut_a(LOG_BUFFER_SIZE >= 16 * OS_FILE_LOG_BLOCK_SIZE);
  ut_a(LOG_BUFFER_SIZE >= 4 * UNIV_PAGE_SIZE);

  buf = ut_malloc(LOG_BUFFER_SIZE + OS_FILE_LOG_BLOCK_SIZE);
  log_sys->buf = ut_align(buf, OS_FILE_LOG_BLOCK_SIZE);

  log_sys->buf_size = LOG_BUFFER_SIZE;

  memset(log_sys->buf, '\0', LOG_BUFFER_SIZE);

  log_sys->max_buf_free = log_sys->buf_size / LOG_BUF_FLUSH_RATIO - LOG_BUF_FLUSH_MARGIN;
  log_sys->check_flush_or_checkpoint = TRUE;
  UT_LIST_INIT(log_sys->log_groups);

  log_sys->n_log_ios = 0;

  log_sys->n_log_ios_old = log_sys->n_log_ios;
  log_sys->last_printout_time = time(NULL);
  /*----------------------------*/

  log_sys->buf_next_to_write = 0;

  log_sys->write_lsn = ut_dulint_zero;
  log_sys->current_flush_lsn = ut_dulint_zero;
  log_sys->flushed_to_disk_lsn = ut_dulint_zero;

  log_sys->written_to_some_lsn = log_sys->lsn;
  log_sys->written_to_all_lsn = log_sys->lsn;

  log_sys->n_pending_writes = 0;

  log_sys->no_flush_event = os_event_create(NULL);

  os_event_set(log_sys->no_flush_event);

  log_sys->one_flushed_event = os_event_create(NULL);

  os_event_set(log_sys->one_flushed_event);

  /*----------------------------*/
  log_sys->adm_checkpoint_interval = ULINT_MAX;

  log_sys->next_checkpoint_no = ut_dulint_zero;
  log_sys->last_checkpoint_lsn = log_sys->lsn;
  log_sys->n_pending_checkpoint_writes = 0;

  rw_lock_create(&(log_sys->checkpoint_lock));
  rw_lock_set_level(&(log_sys->checkpoint_lock), SYNC_NO_ORDER_CHECK);

  log_sys->checkpoint_buf = ut_align(mem_alloc(2 * OS_FILE_LOG_BLOCK_SIZE), OS_FILE_LOG_BLOCK_SIZE);
  memset(log_sys->checkpoint_buf, '\0', OS_FILE_LOG_BLOCK_SIZE);
  /*----------------------------*/

#ifdef UNIV_LOG_ARCHIVE
  /* Under MySQL, log archiving is always off */
  log_sys->archiving_state = LOG_ARCH_OFF;
  log_sys->archived_lsn = log_sys->lsn;
  log_sys->next_archived_lsn = ut_dulint_zero;

  log_sys->n_pending_archive_ios = 0;

  rw_lock_create(&(log_sys->archive_lock));
  rw_lock_set_level(&(log_sys->archive_lock), SYNC_NO_ORDER_CHECK);

  log_sys->archive_buf = NULL;

  /* ut_align(
          ut_malloc(LOG_ARCHIVE_BUF_SIZE
                    + OS_FILE_LOG_BLOCK_SIZE),
                          OS_FILE_LOG_BLOCK_SIZE); */
  log_sys->archive_buf_size = 0;

  /* memset(log_sys->archive_buf, '\0', LOG_ARCHIVE_BUF_SIZE); */

  log_sys->archiving_on = os_event_create(NULL);
#endif /* UNIV_LOG_ARCHIVE */

  /*----------------------------*/

  log_block_init(log_sys->buf, log_sys->lsn);
  log_block_set_first_rec_group(log_sys->buf, LOG_BLOCK_HDR_SIZE);

  log_sys->buf_free = LOG_BLOCK_HDR_SIZE;
  log_sys->lsn = ut_dulint_add(LOG_START_LSN, LOG_BLOCK_HDR_SIZE);

  mutex_exit(&(log_sys->mutex));

#ifdef UNIV_LOG_DEBUG
  recv_sys_create();
  recv_sys_init(FALSE, buf_pool_get_curr_size());

  recv_sys->parse_start_lsn = log_sys->lsn;
  recv_sys->scanned_lsn = log_sys->lsn;
  recv_sys->scanned_checkpoint_no = 0;
  recv_sys->recovered_lsn = log_sys->lsn;
  recv_sys->limit_lsn = ut_dulint_max;
#endif
}

/**********************************************************************
Inits a log group to the log system. */

void log_group_init(
    /*===========*/
    ulint id,        /* in: group id */
    ulint n_files,   /* in: number of log files */
    ulint file_size, /* in: log file size in bytes */
    ulint space_id,  /* in: space id of the file space
                     which contains the log files of this
                     group */
    ulint archive_space_id __attribute__((unused)))
/* in: space id of the file space
which contains some archived log
files for this group; currently, only
for the first log group this is
used */
{
  ulint i;

  log_group_t *group;

  group = mem_alloc(sizeof(log_group_t));

  group->id = id;
  group->n_files = n_files;
  group->file_size = file_size;
  group->space_id = space_id;
  group->state = LOG_GROUP_OK;
  group->lsn = LOG_START_LSN;
  group->lsn_offset = LOG_FILE_HDR_SIZE;
  group->n_pending_writes = 0;

  group->file_header_bufs = mem_alloc(sizeof(byte *) * n_files);
#ifdef UNIV_LOG_ARCHIVE
  group->archive_file_header_bufs = mem_alloc(sizeof(byte *) * n_files);
#endif /* UNIV_LOG_ARCHIVE */

  for (i = 0; i < n_files; i++)
  {
    *(group->file_header_bufs + i) =
        ut_align(mem_alloc(LOG_FILE_HDR_SIZE + OS_FILE_LOG_BLOCK_SIZE), OS_FILE_LOG_BLOCK_SIZE);

    memset(*(group->file_header_bufs + i), '\0', LOG_FILE_HDR_SIZE);

#ifdef UNIV_LOG_ARCHIVE
    *(group->archive_file_header_bufs + i) =
        ut_align(mem_alloc(LOG_FILE_HDR_SIZE + OS_FILE_LOG_BLOCK_SIZE), OS_FILE_LOG_BLOCK_SIZE);
    memset(*(group->archive_file_header_bufs + i), '\0', LOG_FILE_HDR_SIZE);
#endif /* UNIV_LOG_ARCHIVE */
  }

#ifdef UNIV_LOG_ARCHIVE
  group->archive_space_id = archive_space_id;

  group->archived_file_no = 0;
  group->archived_offset = 0;
#endif /* UNIV_LOG_ARCHIVE */

  group->checkpoint_buf = ut_align(mem_alloc(2 * OS_FILE_LOG_BLOCK_SIZE), OS_FILE_LOG_BLOCK_SIZE);

  memset(group->checkpoint_buf, '\0', OS_FILE_LOG_BLOCK_SIZE);

  UT_LIST_ADD_LAST(log_groups, log_sys->log_groups, group);

  ut_a(log_calc_max_ages());
}

/**********************************************************************
Does the unlockings needed in flush i/o completion. */
UNIV_INLINE
void log_flush_do_unlocks(
    /*=================*/
    ulint code) /* in: any ORed combination of LOG_UNLOCK_FLUSH_LOCK
                and LOG_UNLOCK_NONE_FLUSHED_LOCK */
{
#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  /* NOTE that we must own the log mutex when doing the setting of the
  events: this is because transactions will wait for these events to
  be set, and at that moment the log flush they were waiting for must
  have ended. If the log mutex were not reserved here, the i/o-thread
  calling this function might be preempted for a while, and when it
  resumed execution, it might be that a new flush had been started, and
  this function would erroneously signal the NEW flush as completed.
          Thus, the changes in the state of these events are performed
  atomically in conjunction with the changes in the state of
  log_sys->n_pending_writes etc. */

  if (code & LOG_UNLOCK_NONE_FLUSHED_LOCK)
  {
    os_event_set(log_sys->one_flushed_event);
  }

  if (code & LOG_UNLOCK_FLUSH_LOCK)
  {
    os_event_set(log_sys->no_flush_event);
  }
}

/**********************************************************************
Checks if a flush is completed for a log group and does the completion
routine if yes. */
UNIV_INLINE
ulint log_group_check_flush_completion(
    /*=============================*/
    /* out: LOG_UNLOCK_NONE_FLUSHED_LOCK or 0 */
    log_group_t *group) /* in: log group */
{
#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  if (!log_sys->one_flushed && group->n_pending_writes == 0)
  {
#ifdef UNIV_DEBUG
    if (log_debug_writes)
    {
      fprintf(stderr, "Log flushed first to group %lu\n", (ulong)group->id);
    }
#endif /* UNIV_DEBUG */
    log_sys->written_to_some_lsn = log_sys->write_lsn;
    log_sys->one_flushed = TRUE;

    return (LOG_UNLOCK_NONE_FLUSHED_LOCK);
  }

#ifdef UNIV_DEBUG
  if (log_debug_writes && (group->n_pending_writes == 0))
  {
    fprintf(stderr, "Log flushed to group %lu\n", (ulong)group->id);
  }
#endif /* UNIV_DEBUG */
  return (0);
}

/**********************************************************
Checks if a flush is completed and does the completion routine if yes. */
static ulint log_sys_check_flush_completion(void)
/*================================*/
/* out: LOG_UNLOCK_FLUSH_LOCK or 0 */
{
  ulint move_start;
  ulint move_end;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  if (log_sys->n_pending_writes == 0)
  {
    log_sys->written_to_all_lsn = log_sys->write_lsn;
    log_sys->buf_next_to_write = log_sys->write_end_offset;

    if (log_sys->write_end_offset > log_sys->max_buf_free / 2)
    {
      /* Move the log buffer content to the start of the
      buffer */

      move_start = ut_calc_align_down(log_sys->write_end_offset, OS_FILE_LOG_BLOCK_SIZE);
      move_end = ut_calc_align(log_sys->buf_free, OS_FILE_LOG_BLOCK_SIZE);

      ut_memmove(log_sys->buf, log_sys->buf + move_start, move_end - move_start);
      log_sys->buf_free -= move_start;

      log_sys->buf_next_to_write -= move_start;
    }

    return (LOG_UNLOCK_FLUSH_LOCK);
  }

  return (0);
}

/**********************************************************
Completes an i/o to a log file. */

void log_io_complete(
    /*============*/
    log_group_t *group) /* in: log group or a dummy pointer */
{
  ulint unlock;

#ifdef UNIV_LOG_ARCHIVE
  if ((byte *)group == &log_archive_io)
  {
    /* It was an archive write */

    log_io_complete_archive();

    return;
  }
#endif /* UNIV_LOG_ARCHIVE */

  if ((ulint)group & 0x1UL)
  {
    /* It was a checkpoint write */
    group = (log_group_t *)((ulint)group - 1);

    if (srv_unix_file_flush_method != SRV_UNIX_O_DSYNC && srv_unix_file_flush_method != SRV_UNIX_NOSYNC)
    {
      fil_flush(group->space_id);
    }

#ifdef UNIV_DEBUG
    if (log_debug_writes)
    {
      fprintf(stderr, "Checkpoint info written to group %lu\n", group->id);
    }
#endif /* UNIV_DEBUG */
    log_io_complete_checkpoint();

    return;
  }

  ut_error; /* We currently use synchronous writing of the
            logs and cannot end up here! */

  if (srv_unix_file_flush_method != SRV_UNIX_O_DSYNC && srv_unix_file_flush_method != SRV_UNIX_NOSYNC &&
      srv_flush_log_at_trx_commit != 2)
  {
    fil_flush(group->space_id);
  }

  mutex_enter(&(log_sys->mutex));

  ut_a(group->n_pending_writes > 0);
  ut_a(log_sys->n_pending_writes > 0);

  group->n_pending_writes--;
  log_sys->n_pending_writes--;

  unlock = log_group_check_flush_completion(group);
  unlock = unlock | log_sys_check_flush_completion();

  log_flush_do_unlocks(unlock);

  mutex_exit(&(log_sys->mutex));
}

/**********************************************************
Writes a log file header to a log file space. */
static void log_group_file_header_flush(
    /*========================*/
    log_group_t *group, /* in: log group */
    ulint nth_file,     /* in: header to the nth file in the
                        log file space */
    dulint start_lsn)   /* in: log file data starts at this
                        lsn */
{
  byte *buf;
  ulint dest_offset;
#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  ut_a(nth_file < group->n_files);

  buf = *(group->file_header_bufs + nth_file);

  mach_write_to_4(buf + LOG_GROUP_ID, group->id);
  mach_write_to_8(buf + LOG_FILE_START_LSN, start_lsn);

  /* Wipe over possible label of ibbackup --restore */
  memcpy(buf + LOG_FILE_WAS_CREATED_BY_HOT_BACKUP, "    ", 4);

  dest_offset = nth_file * group->file_size;

#ifdef UNIV_DEBUG
  if (log_debug_writes)
  {
    fprintf(stderr, "Writing log file header to group %lu file %lu\n", (ulong)group->id, (ulong)nth_file);
  }
#endif /* UNIV_DEBUG */
  if (log_do_write)
  {
    log_sys->n_log_ios++;

    srv_os_log_pending_writes++;

    fil_io(OS_FILE_WRITE | OS_FILE_LOG, TRUE, group->space_id, dest_offset / UNIV_PAGE_SIZE,
           dest_offset % UNIV_PAGE_SIZE, OS_FILE_LOG_BLOCK_SIZE, buf, group);

    srv_os_log_pending_writes--;
  }
}

/**********************************************************
Stores a 4-byte checksum to the trailer checksum field of a log block
before writing it to a log file. This checksum is used in recovery to
check the consistency of a log block. */
static void log_block_store_checksum(
    /*=====================*/
    byte *block) /* in/out: pointer to a log block */
{
  log_block_set_checksum(block, log_block_calc_checksum(block));
}

/**********************************************************
Writes a buffer to a log file group. */

void log_group_write_buf(
    /*================*/
    log_group_t *group,    /* in: log group */
    byte *buf,             /* in: buffer */
    ulint len,             /* in: buffer len; must be divisible
                           by OS_FILE_LOG_BLOCK_SIZE */
    dulint start_lsn,      /* in: start lsn of the buffer; must
                           be divisible by
                           OS_FILE_LOG_BLOCK_SIZE */
    ulint new_data_offset) /* in: start offset of new data in
                           buf: this parameter is used to decide
                           if we have to write a new log file
                           header */
{
  ulint write_len;
  ibool write_header;
  ulint next_offset;
  ulint i;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */
  ut_a(len % OS_FILE_LOG_BLOCK_SIZE == 0);
  ut_a(ut_dulint_get_low(start_lsn) % OS_FILE_LOG_BLOCK_SIZE == 0);

  if (new_data_offset == 0)
  {
    write_header = TRUE;
  }
  else
  {
    write_header = FALSE;
  }
loop:
  if (len == 0)
  {
    return;
  }

  next_offset = log_group_calc_lsn_offset(start_lsn, group);

  if ((next_offset % group->file_size == LOG_FILE_HDR_SIZE) && write_header)
  {
    /* We start to write a new log file instance in the group */

    log_group_file_header_flush(group, next_offset / group->file_size, start_lsn);
    srv_os_log_written += OS_FILE_LOG_BLOCK_SIZE;
    srv_log_writes++;
  }

  if ((next_offset % group->file_size) + len > group->file_size)
  {
    write_len = group->file_size - (next_offset % group->file_size);
  }
  else
  {
    write_len = len;
  }

#ifdef UNIV_DEBUG
  if (log_debug_writes)
  {
    fprintf(stderr,
            "Writing log file segment to group %lu offset %lu len %lu\n"
            "start lsn %lu %lu\n"
            "First block n:o %lu last block n:o %lu\n",
            (ulong)group->id, (ulong)next_offset, (ulong)write_len, (ulong)ut_dulint_get_high(start_lsn),
            (ulong)ut_dulint_get_low(start_lsn), (ulong)log_block_get_hdr_no(buf),
            (ulong)log_block_get_hdr_no(buf + write_len - OS_FILE_LOG_BLOCK_SIZE));
    ut_a(log_block_get_hdr_no(buf) == log_block_convert_lsn_to_no(start_lsn));

    for (i = 0; i < write_len / OS_FILE_LOG_BLOCK_SIZE; i++)
    {
      ut_a(log_block_get_hdr_no(buf) + i == log_block_get_hdr_no(buf + i * OS_FILE_LOG_BLOCK_SIZE));
    }
  }
#endif /* UNIV_DEBUG */
  /* Calculate the checksums for each log block and write them to
  the trailer fields of the log blocks */

  for (i = 0; i < write_len / OS_FILE_LOG_BLOCK_SIZE; i++)
  {
    log_block_store_checksum(buf + i * OS_FILE_LOG_BLOCK_SIZE);
  }

  if (log_do_write)
  {
    log_sys->n_log_ios++;

    srv_os_log_pending_writes++;

    fil_io(OS_FILE_WRITE | OS_FILE_LOG, TRUE, group->space_id, next_offset / UNIV_PAGE_SIZE,
           next_offset % UNIV_PAGE_SIZE, write_len, buf, group);

    srv_os_log_pending_writes--;

    srv_os_log_written += write_len;
    srv_log_writes++;
  }

  if (write_len < len)
  {
    start_lsn = ut_dulint_add(start_lsn, write_len);
    len -= write_len;
    buf += write_len;

    write_header = TRUE;

    goto loop;
  }
}

/**********************************************************
This function is called, e.g., when a transaction wants to commit. It checks
that the log has been written to the log file up to the last log entry written
by the transaction. If there is a flush running, it waits and checks if the
flush flushed enough. If not, starts a new flush. */

void log_write_up_to(
    /*============*/
    dulint lsn, /* in: log sequence number up to which the log should
                be written, ut_dulint_max if not specified */
    ulint wait, /* in: LOG_NO_WAIT, LOG_WAIT_ONE_GROUP,
                or LOG_WAIT_ALL_GROUPS */
    ibool flush_to_disk)
/* in: TRUE if we want the written log also to be
flushed to disk */
{
  log_group_t *group;
  ulint start_offset;
  ulint end_offset;
  ulint area_start;
  ulint area_end;
  ulint loop_count;
  ulint unlock;

  if (recv_no_ibuf_operations)
  {
    /* Recovery is running and no operations on the log files are
    allowed yet (the variable name .._no_ibuf_.. is misleading) */

    return;
  }

  loop_count = 0;
loop:
  loop_count++;

  ut_ad(loop_count < 5);

  if (loop_count > 2)
  {
    /*		fprintf(stderr, "Log loop count %lu\n", loop_count); */
  }

  mutex_enter(&(log_sys->mutex));

  if (flush_to_disk && ut_dulint_cmp(log_sys->flushed_to_disk_lsn, lsn) >= 0)
  {
    mutex_exit(&(log_sys->mutex));

    return;
  }

  if (!flush_to_disk && (ut_dulint_cmp(log_sys->written_to_all_lsn, lsn) >= 0 ||
                         (ut_dulint_cmp(log_sys->written_to_some_lsn, lsn) >= 0 && wait != LOG_WAIT_ALL_GROUPS)))
  {
    mutex_exit(&(log_sys->mutex));

    return;
  }

  if (log_sys->n_pending_writes > 0)
  {
    /* A write (+ possibly flush to disk) is running */

    if (flush_to_disk && ut_dulint_cmp(log_sys->current_flush_lsn, lsn) >= 0)
    {
      /* The write + flush will write enough: wait for it to
      complete  */

      goto do_waits;
    }

    if (!flush_to_disk && ut_dulint_cmp(log_sys->write_lsn, lsn) >= 0)
    {
      /* The write will write enough: wait for it to
      complete  */

      goto do_waits;
    }

    mutex_exit(&(log_sys->mutex));

    /* Wait for the write to complete and try to start a new
    write */

    os_event_wait(log_sys->no_flush_event);

    goto loop;
  }

  if (!flush_to_disk && log_sys->buf_free == log_sys->buf_next_to_write)
  {
    /* Nothing to write and no flush to disk requested */

    mutex_exit(&(log_sys->mutex));

    return;
  }

#ifdef UNIV_DEBUG
  if (log_debug_writes)
  {
    fprintf(stderr, "Writing log from %lu %lu up to lsn %lu %lu\n",
            (ulong)ut_dulint_get_high(log_sys->written_to_all_lsn),
            (ulong)ut_dulint_get_low(log_sys->written_to_all_lsn), (ulong)ut_dulint_get_high(log_sys->lsn),
            (ulong)ut_dulint_get_low(log_sys->lsn));
  }
#endif /* UNIV_DEBUG */
  log_sys->n_pending_writes++;

  group = UT_LIST_GET_FIRST(log_sys->log_groups);
  group->n_pending_writes++; /* We assume here that we have only
                             one log group! */

  os_event_reset(log_sys->no_flush_event);
  os_event_reset(log_sys->one_flushed_event);

  start_offset = log_sys->buf_next_to_write;
  end_offset = log_sys->buf_free;

  area_start = ut_calc_align_down(start_offset, OS_FILE_LOG_BLOCK_SIZE);
  area_end = ut_calc_align(end_offset, OS_FILE_LOG_BLOCK_SIZE);

  ut_ad(area_end - area_start > 0);

  log_sys->write_lsn = log_sys->lsn;

  if (flush_to_disk)
  {
    log_sys->current_flush_lsn = log_sys->lsn;
  }

  log_sys->one_flushed = FALSE;

  log_block_set_flush_bit(log_sys->buf + area_start, TRUE);
  log_block_set_checkpoint_no(log_sys->buf + area_end - OS_FILE_LOG_BLOCK_SIZE, log_sys->next_checkpoint_no);

  /* Copy the last, incompletely written, log block a log block length
  up, so that when the flush operation writes from the log buffer, the
  segment to write will not be changed by writers to the log */

  ut_memcpy(log_sys->buf + area_end, log_sys->buf + area_end - OS_FILE_LOG_BLOCK_SIZE, OS_FILE_LOG_BLOCK_SIZE);

  log_sys->buf_free += OS_FILE_LOG_BLOCK_SIZE;
  log_sys->write_end_offset = log_sys->buf_free;

  group = UT_LIST_GET_FIRST(log_sys->log_groups);

  /* Do the write to the log files */

  while (group)
  {
    log_group_write_buf(group, log_sys->buf + area_start, area_end - area_start,
                        ut_dulint_align_down(log_sys->written_to_all_lsn, OS_FILE_LOG_BLOCK_SIZE),
                        start_offset - area_start);

    log_group_set_fields(group, log_sys->write_lsn);

    group = UT_LIST_GET_NEXT(log_groups, group);
  }

  mutex_exit(&(log_sys->mutex));

  if (srv_unix_file_flush_method == SRV_UNIX_O_DSYNC)
  {
    /* O_DSYNC means the OS did not buffer the log file at all:
    so we have also flushed to disk what we have written */

    log_sys->flushed_to_disk_lsn = log_sys->write_lsn;
  }
  else if (flush_to_disk)
  {
    group = UT_LIST_GET_FIRST(log_sys->log_groups);

    fil_flush(group->space_id);
    log_sys->flushed_to_disk_lsn = log_sys->write_lsn;
  }

  mutex_enter(&(log_sys->mutex));

  group = UT_LIST_GET_FIRST(log_sys->log_groups);

  ut_a(group->n_pending_writes == 1);
  ut_a(log_sys->n_pending_writes == 1);

  group->n_pending_writes--;
  log_sys->n_pending_writes--;

  unlock = log_group_check_flush_completion(group);
  unlock = unlock | log_sys_check_flush_completion();

  log_flush_do_unlocks(unlock);

  mutex_exit(&(log_sys->mutex));

  return;

do_waits:
  mutex_exit(&(log_sys->mutex));

  if (wait == LOG_WAIT_ONE_GROUP)
  {
    os_event_wait(log_sys->one_flushed_event);
  }
  else if (wait == LOG_WAIT_ALL_GROUPS)
  {
    os_event_wait(log_sys->no_flush_event);
  }
  else
  {
    ut_ad(wait == LOG_NO_WAIT);
  }
}

/********************************************************************
Does a syncronous flush of the log buffer to disk. */

void log_buffer_flush_to_disk(void)
/*==========================*/
{
  dulint lsn;

  mutex_enter(&(log_sys->mutex));

  lsn = log_sys->lsn;

  mutex_exit(&(log_sys->mutex));

  log_write_up_to(lsn, LOG_WAIT_ALL_GROUPS, TRUE);
}

/********************************************************************
Tries to establish a big enough margin of free space in the log buffer, such
that a new log entry can be catenated without an immediate need for a flush. */
static void log_flush_margin(void)
/*==================*/
{
  ibool do_flush = FALSE;
  log_t *log = log_sys;
  dulint lsn;

  mutex_enter(&(log->mutex));

  if (log->buf_free > log->max_buf_free)
  {
    if (log->n_pending_writes > 0)
    {
      /* A flush is running: hope that it will provide enough
      free space */
    }
    else
    {
      do_flush = TRUE;
      lsn = log->lsn;
    }
  }

  mutex_exit(&(log->mutex));

  if (do_flush)
  {
    log_write_up_to(lsn, LOG_NO_WAIT, FALSE);
  }
}

/********************************************************************
Advances the smallest lsn for which there are unflushed dirty blocks in the
buffer pool. NOTE: this function may only be called if the calling thread owns
no synchronization objects! */

ibool log_preflush_pool_modified_pages(
    /*=============================*/
    /* out: FALSE if there was a flush batch of
    the same type running, which means that we
    could not start this flush batch */
    dulint new_oldest, /* in: try to advance oldest_modified_lsn
                       at least to this lsn */
    ibool sync)        /* in: TRUE if synchronous operation is
                       desired */
{
  ulint n_pages;

  if (recv_recovery_on)
  {
    /* If the recovery is running, we must first apply all
    log records to their respective file pages to get the
    right modify lsn values to these pages: otherwise, there
    might be pages on disk which are not yet recovered to the
    current lsn, and even after calling this function, we could
    not know how up-to-date the disk version of the database is,
    and we could not make a new checkpoint on the basis of the
    info on the buffer pool only. */

    recv_apply_hashed_log_recs(TRUE);
  }

  n_pages = buf_flush_batch(BUF_FLUSH_LIST, ULINT_MAX, new_oldest);

  if (sync)
  {
    buf_flush_wait_batch_end(BUF_FLUSH_LIST);
  }

  if (n_pages == ULINT_UNDEFINED)
  {
    return (FALSE);
  }

  return (TRUE);
}

/**********************************************************
Completes a checkpoint. */
static void log_complete_checkpoint(void)
/*=========================*/
{
#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */
  ut_ad(log_sys->n_pending_checkpoint_writes == 0);

  log_sys->next_checkpoint_no = ut_dulint_add(log_sys->next_checkpoint_no, 1);

  log_sys->last_checkpoint_lsn = log_sys->next_checkpoint_lsn;

  rw_lock_x_unlock_gen(&(log_sys->checkpoint_lock), LOG_CHECKPOINT);
}

/**********************************************************
Completes an asynchronous checkpoint info write i/o to a log file. */
static void log_io_complete_checkpoint(void)
/*============================*/
{
  mutex_enter(&(log_sys->mutex));

  ut_ad(log_sys->n_pending_checkpoint_writes > 0);

  log_sys->n_pending_checkpoint_writes--;

  if (log_sys->n_pending_checkpoint_writes == 0)
  {
    log_complete_checkpoint();
  }

  mutex_exit(&(log_sys->mutex));
}

/***********************************************************************
Writes info to a checkpoint about a log group. */
static void log_checkpoint_set_nth_group_info(
    /*==============================*/
    byte *buf,     /* in: buffer for checkpoint info */
    ulint n,       /* in: nth slot */
    ulint file_no, /* in: archived file number */
    ulint offset)  /* in: archived file offset */
{
  ut_ad(n < LOG_MAX_N_GROUPS);

  mach_write_to_4(buf + LOG_CHECKPOINT_GROUP_ARRAY + 8 * n + LOG_CHECKPOINT_ARCHIVED_FILE_NO, file_no);
  mach_write_to_4(buf + LOG_CHECKPOINT_GROUP_ARRAY + 8 * n + LOG_CHECKPOINT_ARCHIVED_OFFSET, offset);
}

/***********************************************************************
Gets info from a checkpoint about a log group. */

void log_checkpoint_get_nth_group_info(
    /*==============================*/
    byte *buf,      /* in: buffer containing checkpoint info */
    ulint n,        /* in: nth slot */
    ulint *file_no, /* out: archived file number */
    ulint *offset)  /* out: archived file offset */
{
  ut_ad(n < LOG_MAX_N_GROUPS);

  *file_no = mach_read_from_4(buf + LOG_CHECKPOINT_GROUP_ARRAY + 8 * n + LOG_CHECKPOINT_ARCHIVED_FILE_NO);
  *offset = mach_read_from_4(buf + LOG_CHECKPOINT_GROUP_ARRAY + 8 * n + LOG_CHECKPOINT_ARCHIVED_OFFSET);
}

/**********************************************************
Writes the checkpoint info to a log group header. */
static void log_group_checkpoint(
    /*=================*/
    log_group_t *group) /* in: log group */
{
  log_group_t *group2;
#ifdef UNIV_LOG_ARCHIVE
  dulint archived_lsn;
  dulint next_archived_lsn;
#endif /* UNIV_LOG_ARCHIVE */
  ulint write_offset;
  ulint fold;
  byte *buf;
  ulint i;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */
  ut_a(LOG_CHECKPOINT_SIZE <= OS_FILE_LOG_BLOCK_SIZE);

  buf = group->checkpoint_buf;

  mach_write_to_8(buf + LOG_CHECKPOINT_NO, log_sys->next_checkpoint_no);
  mach_write_to_8(buf + LOG_CHECKPOINT_LSN, log_sys->next_checkpoint_lsn);

  mach_write_to_4(buf + LOG_CHECKPOINT_OFFSET, log_group_calc_lsn_offset(log_sys->next_checkpoint_lsn, group));

  mach_write_to_4(buf + LOG_CHECKPOINT_LOG_BUF_SIZE, log_sys->buf_size);

#ifdef UNIV_LOG_ARCHIVE
  if (log_sys->archiving_state == LOG_ARCH_OFF)
  {
    archived_lsn = ut_dulint_max;
  }
  else
  {
    archived_lsn = log_sys->archived_lsn;

    if (0 != ut_dulint_cmp(archived_lsn, log_sys->next_archived_lsn))
    {
      next_archived_lsn = log_sys->next_archived_lsn;
      /* For debugging only */
    }
  }

  mach_write_to_8(buf + LOG_CHECKPOINT_ARCHIVED_LSN, archived_lsn);
#else  /* UNIV_LOG_ARCHIVE */
  mach_write_to_8(buf + LOG_CHECKPOINT_ARCHIVED_LSN, ut_dulint_max);
#endif /* UNIV_LOG_ARCHIVE */

  for (i = 0; i < LOG_MAX_N_GROUPS; i++)
  {
    log_checkpoint_set_nth_group_info(buf, i, 0, 0);
  }

  group2 = UT_LIST_GET_FIRST(log_sys->log_groups);

  while (group2)
  {
    log_checkpoint_set_nth_group_info(buf, group2->id,
#ifdef UNIV_LOG_ARCHIVE
                                      group2->archived_file_no, group2->archived_offset
#else  /* UNIV_LOG_ARCHIVE */
                                      0, 0
#endif /* UNIV_LOG_ARCHIVE */
    );

    group2 = UT_LIST_GET_NEXT(log_groups, group2);
  }

  fold = ut_fold_binary(buf, LOG_CHECKPOINT_CHECKSUM_1);
  mach_write_to_4(buf + LOG_CHECKPOINT_CHECKSUM_1, fold);

  fold = ut_fold_binary(buf + LOG_CHECKPOINT_LSN, LOG_CHECKPOINT_CHECKSUM_2 - LOG_CHECKPOINT_LSN);
  mach_write_to_4(buf + LOG_CHECKPOINT_CHECKSUM_2, fold);

  /* Starting from InnoDB-3.23.50, we also write info on allocated
  size in the tablespace */

  mach_write_to_4(buf + LOG_CHECKPOINT_FSP_FREE_LIMIT, log_fsp_current_free_limit);

  mach_write_to_4(buf + LOG_CHECKPOINT_FSP_MAGIC_N, LOG_CHECKPOINT_FSP_MAGIC_N_VAL);

  /* We alternate the physical place of the checkpoint info in the first
  log file */

  if (ut_dulint_get_low(log_sys->next_checkpoint_no) % 2 == 0)
  {
    write_offset = LOG_CHECKPOINT_1;
  }
  else
  {
    write_offset = LOG_CHECKPOINT_2;
  }

  if (log_do_write)
  {
    if (log_sys->n_pending_checkpoint_writes == 0)
    {
      rw_lock_x_lock_gen(&(log_sys->checkpoint_lock), LOG_CHECKPOINT);
    }

    log_sys->n_pending_checkpoint_writes++;

    log_sys->n_log_ios++;

    /* We send as the last parameter the group machine address
    added with 1, as we want to distinguish between a normal log
    file write and a checkpoint field write */

    fil_io(OS_FILE_WRITE | OS_FILE_LOG, FALSE, group->space_id, write_offset / UNIV_PAGE_SIZE,
           write_offset % UNIV_PAGE_SIZE, OS_FILE_LOG_BLOCK_SIZE, buf, ((byte *)group + 1));

    ut_ad(((ulint)group & 0x1UL) == 0);
  }
}

/**********************************************************
Writes info to a buffer of a log group when log files are created in
backup restoration. */

void log_reset_first_header_and_checkpoint(
    /*==================================*/
    byte *hdr_buf, /* in: buffer which will be written to the start
                   of the first log file */
    dulint start)  /* in: lsn of the start of the first log file;
                   we pretend that there is a checkpoint at
                   start + LOG_BLOCK_HDR_SIZE */
{
  ulint fold;
  byte *buf;
  dulint lsn;

  mach_write_to_4(hdr_buf + LOG_GROUP_ID, 0);
  mach_write_to_8(hdr_buf + LOG_FILE_START_LSN, start);

  lsn = ut_dulint_add(start, LOG_BLOCK_HDR_SIZE);

  /* Write the label of ibbackup --restore */
  strcpy((char *)hdr_buf + LOG_FILE_WAS_CREATED_BY_HOT_BACKUP, "ibbackup ");
  ut_sprintf_timestamp((char *)hdr_buf + (LOG_FILE_WAS_CREATED_BY_HOT_BACKUP + (sizeof "ibbackup ") - 1));
  buf = hdr_buf + LOG_CHECKPOINT_1;

  mach_write_to_8(buf + LOG_CHECKPOINT_NO, ut_dulint_zero);
  mach_write_to_8(buf + LOG_CHECKPOINT_LSN, lsn);

  mach_write_to_4(buf + LOG_CHECKPOINT_OFFSET, LOG_FILE_HDR_SIZE + LOG_BLOCK_HDR_SIZE);

  mach_write_to_4(buf + LOG_CHECKPOINT_LOG_BUF_SIZE, 2 * 1024 * 1024);

  mach_write_to_8(buf + LOG_CHECKPOINT_ARCHIVED_LSN, ut_dulint_max);

  fold = ut_fold_binary(buf, LOG_CHECKPOINT_CHECKSUM_1);
  mach_write_to_4(buf + LOG_CHECKPOINT_CHECKSUM_1, fold);

  fold = ut_fold_binary(buf + LOG_CHECKPOINT_LSN, LOG_CHECKPOINT_CHECKSUM_2 - LOG_CHECKPOINT_LSN);
  mach_write_to_4(buf + LOG_CHECKPOINT_CHECKSUM_2, fold);

  /* Starting from InnoDB-3.23.50, we should also write info on
  allocated size in the tablespace, but unfortunately we do not
  know it here */
}

/**********************************************************
Reads a checkpoint info from a log group header to log_sys->checkpoint_buf. */

void log_group_read_checkpoint_info(
    /*===========================*/
    log_group_t *group, /* in: log group */
    ulint field)        /* in: LOG_CHECKPOINT_1 or LOG_CHECKPOINT_2 */
{
#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  log_sys->n_log_ios++;

  fil_io(OS_FILE_READ | OS_FILE_LOG, TRUE, group->space_id, field / UNIV_PAGE_SIZE, field % UNIV_PAGE_SIZE,
         OS_FILE_LOG_BLOCK_SIZE, log_sys->checkpoint_buf, NULL);
}

/**********************************************************
Writes checkpoint info to groups. */

void log_groups_write_checkpoint_info(void)
/*==================================*/
{
  log_group_t *group;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  group = UT_LIST_GET_FIRST(log_sys->log_groups);

  while (group)
  {
    log_group_checkpoint(group);

    group = UT_LIST_GET_NEXT(log_groups, group);
  }
}

/**********************************************************
Makes a checkpoint. Note that this function does not flush dirty
blocks from the buffer pool: it only checks what is lsn of the oldest
modification in the pool, and writes information about the lsn in
log files. Use log_make_checkpoint_at to flush also the pool. */

ibool log_checkpoint(
    /*===========*/
    /* out: TRUE if success, FALSE if a checkpoint
    write was already running */
    ibool sync,         /* in: TRUE if synchronous operation is
                        desired */
    ibool write_always) /* in: the function normally checks if the
                        the new checkpoint would have a greater
                        lsn than the previous one: if not, then no
                        physical write is done; by setting this
                        parameter TRUE, a physical write will always be
                        made to log files */
{
  dulint oldest_lsn;

  if (recv_recovery_is_on())
  {
    recv_apply_hashed_log_recs(TRUE);
  }

  if (srv_unix_file_flush_method != SRV_UNIX_NOSYNC)
  {
    fil_flush_file_spaces(FIL_TABLESPACE);
  }

  mutex_enter(&(log_sys->mutex));

  oldest_lsn = log_buf_pool_get_oldest_modification();

  mutex_exit(&(log_sys->mutex));

  /* Because log also contains headers and dummy log records,
  if the buffer pool contains no dirty buffers, oldest_lsn
  gets the value log_sys->lsn from the previous function,
  and we must make sure that the log is flushed up to that
  lsn. If there are dirty buffers in the buffer pool, then our
  write-ahead-logging algorithm ensures that the log has been flushed
  up to oldest_lsn. */

  log_write_up_to(oldest_lsn, LOG_WAIT_ALL_GROUPS, TRUE);

  mutex_enter(&(log_sys->mutex));

  if (!write_always && ut_dulint_cmp(log_sys->last_checkpoint_lsn, oldest_lsn) >= 0)
  {
    mutex_exit(&(log_sys->mutex));

    return (TRUE);
  }

  ut_ad(ut_dulint_cmp(log_sys->written_to_all_lsn, oldest_lsn) >= 0);

  if (log_sys->n_pending_checkpoint_writes > 0)
  {
    /* A checkpoint write is running */

    mutex_exit(&(log_sys->mutex));

    if (sync)
    {
      /* Wait for the checkpoint write to complete */
      rw_lock_s_lock(&(log_sys->checkpoint_lock));
      rw_lock_s_unlock(&(log_sys->checkpoint_lock));
    }

    return (FALSE);
  }

  log_sys->next_checkpoint_lsn = oldest_lsn;

#ifdef UNIV_DEBUG
  if (log_debug_writes)
  {
    fprintf(stderr, "Making checkpoint no %lu at lsn %lu %lu\n", (ulong)ut_dulint_get_low(log_sys->next_checkpoint_no),
            (ulong)ut_dulint_get_high(oldest_lsn), (ulong)ut_dulint_get_low(oldest_lsn));
  }
#endif /* UNIV_DEBUG */

  log_groups_write_checkpoint_info();

  mutex_exit(&(log_sys->mutex));

  if (sync)
  {
    /* Wait for the checkpoint write to complete */
    rw_lock_s_lock(&(log_sys->checkpoint_lock));
    rw_lock_s_unlock(&(log_sys->checkpoint_lock));
  }

  return (TRUE);
}

/********************************************************************
Makes a checkpoint at a given lsn or later. */

void log_make_checkpoint_at(
    /*===================*/
    dulint lsn,         /* in: make a checkpoint at this or a later
                        lsn, if ut_dulint_max, makes a checkpoint at
                        the latest lsn */
    ibool write_always) /* in: the function normally checks if the
                        the new checkpoint would have a greater
                        lsn than the previous one: if not, then no
                        physical write is done; by setting this
                        parameter TRUE, a physical write will always be
                        made to log files */
{
  ibool success;

  /* Preflush pages synchronously */

  success = FALSE;

  while (!success)
  {
    success = log_preflush_pool_modified_pages(lsn, TRUE);
  }

  success = FALSE;

  while (!success)
  {
    success = log_checkpoint(TRUE, write_always);
  }
}

/********************************************************************
Tries to establish a big enough margin of free space in the log groups, such
that a new log entry can be catenated without an immediate need for a
checkpoint. NOTE: this function may only be called if the calling thread
owns no synchronization objects! */
static void log_checkpoint_margin(void)
/*=======================*/
{
  log_t *log = log_sys;
  ulint age;
  ulint checkpoint_age;
  ulint advance;
  dulint oldest_lsn;
  ibool sync;
  ibool checkpoint_sync;
  ibool do_checkpoint;
  ibool success;
loop:
  sync = FALSE;
  checkpoint_sync = FALSE;
  do_checkpoint = FALSE;

  mutex_enter(&(log->mutex));

  if (log->check_flush_or_checkpoint == FALSE)
  {
    mutex_exit(&(log->mutex));

    return;
  }

  oldest_lsn = log_buf_pool_get_oldest_modification();

  age = ut_dulint_minus(log->lsn, oldest_lsn);

  if (age > log->max_modified_age_sync)
  {
    /* A flush is urgent: we have to do a synchronous preflush */

    sync = TRUE;
    advance = 2 * (age - log->max_modified_age_sync);
  }
  else if (age > log->max_modified_age_async)
  {
    /* A flush is not urgent: we do an asynchronous preflush */
    advance = age - log->max_modified_age_async;
  }
  else
  {
    advance = 0;
  }

  checkpoint_age = ut_dulint_minus(log->lsn, log->last_checkpoint_lsn);

  if (checkpoint_age > log->max_checkpoint_age)
  {
    /* A checkpoint is urgent: we do it synchronously */

    checkpoint_sync = TRUE;

    do_checkpoint = TRUE;
  }
  else if (checkpoint_age > log->max_checkpoint_age_async)
  {
    /* A checkpoint is not urgent: do it asynchronously */

    do_checkpoint = TRUE;

    log->check_flush_or_checkpoint = FALSE;
  }
  else
  {
    log->check_flush_or_checkpoint = FALSE;
  }

  mutex_exit(&(log->mutex));

  if (advance)
  {
    dulint new_oldest = ut_dulint_add(oldest_lsn, advance);

    success = log_preflush_pool_modified_pages(new_oldest, sync);

    /* If the flush succeeded, this thread has done its part
    and can proceed. If it did not succeed, there was another
    thread doing a flush at the same time. If sync was FALSE,
    the flush was not urgent, and we let this thread proceed.
    Otherwise, we let it start from the beginning again. */

    if (sync && !success)
    {
      mutex_enter(&(log->mutex));

      log->check_flush_or_checkpoint = TRUE;

      mutex_exit(&(log->mutex));
      goto loop;
    }
  }

  if (do_checkpoint)
  {
    log_checkpoint(checkpoint_sync, FALSE);

    if (checkpoint_sync)
    {
      goto loop;
    }
  }
}

/**********************************************************
Reads a specified log segment to a buffer. */

void log_group_read_log_seg(
    /*===================*/
    ulint type,         /* in: LOG_ARCHIVE or LOG_RECOVER */
    byte *buf,          /* in: buffer where to read */
    log_group_t *group, /* in: log group */
    dulint start_lsn,   /* in: read area start */
    dulint end_lsn)     /* in: read area end */
{
  ulint len;
  ulint source_offset;
  ibool sync;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  sync = FALSE;

  if (type == LOG_RECOVER)
  {
    sync = TRUE;
  }
loop:
  source_offset = log_group_calc_lsn_offset(start_lsn, group);

  len = ut_dulint_minus(end_lsn, start_lsn);

  ut_ad(len != 0);

  if ((source_offset % group->file_size) + len > group->file_size)
  {
    len = group->file_size - (source_offset % group->file_size);
  }

#ifdef UNIV_LOG_ARCHIVE
  if (type == LOG_ARCHIVE)
  {
    log_sys->n_pending_archive_ios++;
  }
#endif /* UNIV_LOG_ARCHIVE */

  log_sys->n_log_ios++;

  fil_io(OS_FILE_READ | OS_FILE_LOG, sync, group->space_id, source_offset / UNIV_PAGE_SIZE,
         source_offset % UNIV_PAGE_SIZE, len, buf, NULL);

  start_lsn = ut_dulint_add(start_lsn, len);
  buf += len;

  if (ut_dulint_cmp(start_lsn, end_lsn) != 0)
  {
    goto loop;
  }
}

#ifdef UNIV_LOG_ARCHIVE
/**********************************************************
Generates an archived log file name. */

void log_archived_file_name_gen(
    /*=======================*/
    char *buf, /* in: buffer where to write */
    ulint id __attribute__((unused)),
    /* in: group id;
    currently we only archive the first group */
    ulint file_no) /* in: file number */
{
  sprintf(buf, "%sib_arch_log_%010lu", srv_arch_dir, (ulong)file_no);
}

/**********************************************************
Writes a log file header to a log file space. */
static void log_group_archive_file_header_write(
    /*================================*/
    log_group_t *group, /* in: log group */
    ulint nth_file,     /* in: header to the nth file in the
                        archive log file space */
    ulint file_no,      /* in: archived file number */
    dulint start_lsn)   /* in: log file data starts at this
                        lsn */
{
  byte *buf;
  ulint dest_offset;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  ut_a(nth_file < group->n_files);

  buf = *(group->archive_file_header_bufs + nth_file);

  mach_write_to_4(buf + LOG_GROUP_ID, group->id);
  mach_write_to_8(buf + LOG_FILE_START_LSN, start_lsn);
  mach_write_to_4(buf + LOG_FILE_NO, file_no);

  mach_write_to_4(buf + LOG_FILE_ARCH_COMPLETED, FALSE);

  dest_offset = nth_file * group->file_size;

  log_sys->n_log_ios++;

  fil_io(OS_FILE_WRITE | OS_FILE_LOG, TRUE, group->archive_space_id, dest_offset / UNIV_PAGE_SIZE,
         dest_offset % UNIV_PAGE_SIZE, 2 * OS_FILE_LOG_BLOCK_SIZE, buf, &log_archive_io);
}

/**********************************************************
Writes a log file header to a completed archived log file. */
static void log_group_archive_completed_header_write(
    /*=====================================*/
    log_group_t *group, /* in: log group */
    ulint nth_file,     /* in: header to the nth file in the
                        archive log file space */
    dulint end_lsn)     /* in: end lsn of the file */
{
  byte *buf;
  ulint dest_offset;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */
  ut_a(nth_file < group->n_files);

  buf = *(group->archive_file_header_bufs + nth_file);

  mach_write_to_4(buf + LOG_FILE_ARCH_COMPLETED, TRUE);
  mach_write_to_8(buf + LOG_FILE_END_LSN, end_lsn);

  dest_offset = nth_file * group->file_size + LOG_FILE_ARCH_COMPLETED;

  log_sys->n_log_ios++;

  fil_io(OS_FILE_WRITE | OS_FILE_LOG, TRUE, group->archive_space_id, dest_offset / UNIV_PAGE_SIZE,
         dest_offset % UNIV_PAGE_SIZE, OS_FILE_LOG_BLOCK_SIZE, buf + LOG_FILE_ARCH_COMPLETED, &log_archive_io);
}

/**********************************************************
Does the archive writes for a single log group. */
static void log_group_archive(
    /*==============*/
    log_group_t *group) /* in: log group */
{
  os_file_t file_handle;
  dulint start_lsn;
  dulint end_lsn;
  char name[1024];
  byte *buf;
  ulint len;
  ibool ret;
  ulint next_offset;
  ulint n_files;
  ulint open_mode;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  start_lsn = log_sys->archived_lsn;

  ut_a(ut_dulint_get_low(start_lsn) % OS_FILE_LOG_BLOCK_SIZE == 0);

  end_lsn = log_sys->next_archived_lsn;

  ut_a(ut_dulint_get_low(end_lsn) % OS_FILE_LOG_BLOCK_SIZE == 0);

  buf = log_sys->archive_buf;

  n_files = 0;

  next_offset = group->archived_offset;
loop:
  if ((next_offset % group->file_size == 0) || (fil_space_get_size(group->archive_space_id) == 0))
  {
    /* Add the file to the archive file space; create or open the
    file */

    if (next_offset % group->file_size == 0)
    {
      open_mode = OS_FILE_CREATE;
    }
    else
    {
      open_mode = OS_FILE_OPEN;
    }

    log_archived_file_name_gen(name, group->id, group->archived_file_no + n_files);

    file_handle = os_file_create(name, open_mode, OS_FILE_AIO, OS_DATA_FILE, &ret);

    if (!ret && (open_mode == OS_FILE_CREATE))
    {
      file_handle = os_file_create(name, OS_FILE_OPEN, OS_FILE_AIO, OS_DATA_FILE, &ret);
    }

    if (!ret)
    {
      fprintf(stderr,
              "InnoDB: Cannot create or open archive log file %s.\n"
              "InnoDB: Cannot continue operation.\n"
              "InnoDB: Check that the log archive directory exists,\n"
              "InnoDB: you have access rights to it, and\n"
              "InnoDB: there is space available.\n",
              name);
      exit(1);
    }

#ifdef UNIV_DEBUG
    if (log_debug_writes)
    {
      fprintf(stderr, "Created archive file %s\n", name);
    }
#endif /* UNIV_DEBUG */

    ret = os_file_close(file_handle);

    ut_a(ret);

    /* Add the archive file as a node to the space */

    fil_node_create(name, group->file_size / UNIV_PAGE_SIZE, group->archive_space_id, FALSE);

    if (next_offset % group->file_size == 0)
    {
      log_group_archive_file_header_write(group, n_files, group->archived_file_no + n_files, start_lsn);

      next_offset += LOG_FILE_HDR_SIZE;
    }
  }

  len = ut_dulint_minus(end_lsn, start_lsn);

  if (group->file_size < (next_offset % group->file_size) + len)
  {
    len = group->file_size - (next_offset % group->file_size);
  }

#ifdef UNIV_DEBUG
  if (log_debug_writes)
  {
    fprintf(stderr, "Archiving starting at lsn %lu %lu, len %lu to group %lu\n", (ulong)ut_dulint_get_high(start_lsn),
            (ulong)ut_dulint_get_low(start_lsn), (ulong)len, (ulong)group->id);
  }
#endif /* UNIV_DEBUG */

  log_sys->n_pending_archive_ios++;

  log_sys->n_log_ios++;

  fil_io(OS_FILE_WRITE | OS_FILE_LOG, FALSE, group->archive_space_id, next_offset / UNIV_PAGE_SIZE,
         next_offset % UNIV_PAGE_SIZE, ut_calc_align(len, OS_FILE_LOG_BLOCK_SIZE), buf, &log_archive_io);

  start_lsn = ut_dulint_add(start_lsn, len);
  next_offset += len;
  buf += len;

  if (next_offset % group->file_size == 0)
  {
    n_files++;
  }

  if (ut_dulint_cmp(end_lsn, start_lsn) != 0)
  {
    goto loop;
  }

  group->next_archived_file_no = group->archived_file_no + n_files;
  group->next_archived_offset = next_offset % group->file_size;

  ut_a(group->next_archived_offset % OS_FILE_LOG_BLOCK_SIZE == 0);
}

/*********************************************************
(Writes to the archive of each log group.) Currently, only the first
group is archived. */
static void log_archive_groups(void)
/*====================*/
{
  log_group_t *group;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  group = UT_LIST_GET_FIRST(log_sys->log_groups);

  log_group_archive(group);
}

/*********************************************************
Completes the archiving write phase for (each log group), currently,
the first log group. */
static void log_archive_write_complete_groups(void)
/*===================================*/
{
  log_group_t *group;
  ulint end_offset;
  ulint trunc_files;
  ulint n_files;
  dulint start_lsn;
  dulint end_lsn;
  ulint i;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  group = UT_LIST_GET_FIRST(log_sys->log_groups);

  group->archived_file_no = group->next_archived_file_no;
  group->archived_offset = group->next_archived_offset;

  /* Truncate from the archive file space all but the last
  file, or if it has been written full, all files */

  n_files = (UNIV_PAGE_SIZE * fil_space_get_size(group->archive_space_id)) / group->file_size;
  ut_ad(n_files > 0);

  end_offset = group->archived_offset;

  if (end_offset % group->file_size == 0)
  {
    trunc_files = n_files;
  }
  else
  {
    trunc_files = n_files - 1;
  }

#ifdef UNIV_DEBUG
  if (log_debug_writes && trunc_files)
  {
    fprintf(stderr, "Complete file(s) archived to group %lu\n", (ulong)group->id);
  }
#endif /* UNIV_DEBUG */

  /* Calculate the archive file space start lsn */
  start_lsn = ut_dulint_subtract(log_sys->next_archived_lsn,
                                 end_offset - LOG_FILE_HDR_SIZE + trunc_files * (group->file_size - LOG_FILE_HDR_SIZE));
  end_lsn = start_lsn;

  for (i = 0; i < trunc_files; i++)
  {
    end_lsn = ut_dulint_add(end_lsn, group->file_size - LOG_FILE_HDR_SIZE);

    /* Write a notice to the headers of archived log
    files that the file write has been completed */

    log_group_archive_completed_header_write(group, i, end_lsn);
  }

  fil_space_truncate_start(group->archive_space_id, trunc_files * group->file_size);

#ifdef UNIV_DEBUG
  if (log_debug_writes)
  {
    fputs("Archiving writes completed\n", stderr);
  }
#endif /* UNIV_DEBUG */
}

/**********************************************************
Completes an archiving i/o. */
static void log_archive_check_completion_low(void)
/*==================================*/
{
#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  if (log_sys->n_pending_archive_ios == 0 && log_sys->archiving_phase == LOG_ARCHIVE_READ)
  {
#ifdef UNIV_DEBUG
    if (log_debug_writes)
    {
      fputs("Archiving read completed\n", stderr);
    }
#endif /* UNIV_DEBUG */

    /* Archive buffer has now been read in: start archive writes */

    log_sys->archiving_phase = LOG_ARCHIVE_WRITE;

    log_archive_groups();
  }

  if (log_sys->n_pending_archive_ios == 0 && log_sys->archiving_phase == LOG_ARCHIVE_WRITE)
  {
    log_archive_write_complete_groups();

    log_sys->archived_lsn = log_sys->next_archived_lsn;

    rw_lock_x_unlock_gen(&(log_sys->archive_lock), LOG_ARCHIVE);
  }
}

/**********************************************************
Completes an archiving i/o. */
static void log_io_complete_archive(void)
/*=========================*/
{
  log_group_t *group;

  mutex_enter(&(log_sys->mutex));

  group = UT_LIST_GET_FIRST(log_sys->log_groups);

  mutex_exit(&(log_sys->mutex));

  fil_flush(group->archive_space_id);

  mutex_enter(&(log_sys->mutex));

  ut_ad(log_sys->n_pending_archive_ios > 0);

  log_sys->n_pending_archive_ios--;

  log_archive_check_completion_low();

  mutex_exit(&(log_sys->mutex));
}

/************************************************************************
Starts an archiving operation. */

ibool log_archive_do(
    /*===========*/
    /* out: TRUE if succeed, FALSE if an archiving
    operation was already running */
    ibool sync,     /* in: TRUE if synchronous operation is desired */
    ulint *n_bytes) /* out: archive log buffer size, 0 if nothing to
                    archive */
{
  ibool calc_new_limit;
  dulint start_lsn;
  dulint limit_lsn;

  calc_new_limit = TRUE;
loop:
  mutex_enter(&(log_sys->mutex));

  if (log_sys->archiving_state == LOG_ARCH_OFF)
  {
    mutex_exit(&(log_sys->mutex));

    *n_bytes = 0;

    return (TRUE);
  }
  else if (log_sys->archiving_state == LOG_ARCH_STOPPED || log_sys->archiving_state == LOG_ARCH_STOPPING2)
  {
    mutex_exit(&(log_sys->mutex));

    os_event_wait(log_sys->archiving_on);

    mutex_enter(&(log_sys->mutex));

    goto loop;
  }

  start_lsn = log_sys->archived_lsn;

  if (calc_new_limit)
  {
    ut_a(log_sys->archive_buf_size % OS_FILE_LOG_BLOCK_SIZE == 0);
    limit_lsn = ut_dulint_add(start_lsn, log_sys->archive_buf_size);

    *n_bytes = log_sys->archive_buf_size;

    if (ut_dulint_cmp(limit_lsn, log_sys->lsn) >= 0)
    {
      limit_lsn = ut_dulint_align_down(log_sys->lsn, OS_FILE_LOG_BLOCK_SIZE);
    }
  }

  if (ut_dulint_cmp(log_sys->archived_lsn, limit_lsn) >= 0)
  {
    mutex_exit(&(log_sys->mutex));

    *n_bytes = 0;

    return (TRUE);
  }

  if (ut_dulint_cmp(log_sys->written_to_all_lsn, limit_lsn) < 0)
  {
    mutex_exit(&(log_sys->mutex));

    log_write_up_to(limit_lsn, LOG_WAIT_ALL_GROUPS, TRUE);

    calc_new_limit = FALSE;

    goto loop;
  }

  if (log_sys->n_pending_archive_ios > 0)
  {
    /* An archiving operation is running */

    mutex_exit(&(log_sys->mutex));

    if (sync)
    {
      rw_lock_s_lock(&(log_sys->archive_lock));
      rw_lock_s_unlock(&(log_sys->archive_lock));
    }

    *n_bytes = log_sys->archive_buf_size;

    return (FALSE);
  }

  rw_lock_x_lock_gen(&(log_sys->archive_lock), LOG_ARCHIVE);

  log_sys->archiving_phase = LOG_ARCHIVE_READ;

  log_sys->next_archived_lsn = limit_lsn;

#ifdef UNIV_DEBUG
  if (log_debug_writes)
  {
    fprintf(stderr, "Archiving from lsn %lu %lu to lsn %lu %lu\n", (ulong)ut_dulint_get_high(log_sys->archived_lsn),
            (ulong)ut_dulint_get_low(log_sys->archived_lsn), (ulong)ut_dulint_get_high(limit_lsn),
            (ulong)ut_dulint_get_low(limit_lsn));
  }
#endif /* UNIV_DEBUG */

  /* Read the log segment to the archive buffer */

  log_group_read_log_seg(LOG_ARCHIVE, log_sys->archive_buf, UT_LIST_GET_FIRST(log_sys->log_groups), start_lsn,
                         limit_lsn);

  mutex_exit(&(log_sys->mutex));

  if (sync)
  {
    rw_lock_s_lock(&(log_sys->archive_lock));
    rw_lock_s_unlock(&(log_sys->archive_lock));
  }

  *n_bytes = log_sys->archive_buf_size;

  return (TRUE);
}

/********************************************************************
Writes the log contents to the archive at least up to the lsn when this
function was called. */
static void log_archive_all(void)
/*=================*/
{
  dulint present_lsn;
  ulint dummy;

  mutex_enter(&(log_sys->mutex));

  if (log_sys->archiving_state == LOG_ARCH_OFF)
  {
    mutex_exit(&(log_sys->mutex));

    return;
  }

  present_lsn = log_sys->lsn;

  mutex_exit(&(log_sys->mutex));

  log_pad_current_log_block();

  for (;;)
  {
    mutex_enter(&(log_sys->mutex));

    if (ut_dulint_cmp(present_lsn, log_sys->archived_lsn) <= 0)
    {
      mutex_exit(&(log_sys->mutex));

      return;
    }

    mutex_exit(&(log_sys->mutex));

    log_archive_do(TRUE, &dummy);
  }
}

/*********************************************************
Closes the possible open archive log file (for each group) the first group,
and if it was open, increments the group file count by 2, if desired. */
static void log_archive_close_groups(
    /*=====================*/
    ibool increment_file_count) /* in: TRUE if we want to increment
                                the file count */
{
  log_group_t *group;
  ulint trunc_len;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  if (log_sys->archiving_state == LOG_ARCH_OFF)
  {
    return;
  }

  group = UT_LIST_GET_FIRST(log_sys->log_groups);

  trunc_len = UNIV_PAGE_SIZE * fil_space_get_size(group->archive_space_id);
  if (trunc_len > 0)
  {
    ut_a(trunc_len == group->file_size);

    /* Write a notice to the headers of archived log
    files that the file write has been completed */

    log_group_archive_completed_header_write(group, 0, log_sys->archived_lsn);

    fil_space_truncate_start(group->archive_space_id, trunc_len);
    if (increment_file_count)
    {
      group->archived_offset = 0;
      group->archived_file_no += 2;
    }

#ifdef UNIV_DEBUG
    if (log_debug_writes)
    {
      fprintf(stderr, "Incrementing arch file no to %lu in log group %lu\n", (ulong)group->archived_file_no + 2,
              (ulong)group->id);
    }
#endif /* UNIV_DEBUG */
  }
}

/********************************************************************
Writes the log contents to the archive up to the lsn when this function was
called, and stops the archiving. When archiving is started again, the archived
log file numbers start from 2 higher, so that the archiving will not write
again to the archived log files which exist when this function returns. */

ulint log_archive_stop(void)
/*==================*/
/* out: DB_SUCCESS or DB_ERROR */
{
  ibool success;

  mutex_enter(&(log_sys->mutex));

  if (log_sys->archiving_state != LOG_ARCH_ON)
  {
    mutex_exit(&(log_sys->mutex));

    return (DB_ERROR);
  }

  log_sys->archiving_state = LOG_ARCH_STOPPING;

  mutex_exit(&(log_sys->mutex));

  log_archive_all();

  mutex_enter(&(log_sys->mutex));

  log_sys->archiving_state = LOG_ARCH_STOPPING2;
  os_event_reset(log_sys->archiving_on);

  mutex_exit(&(log_sys->mutex));

  /* Wait for a possible archiving operation to end */

  rw_lock_s_lock(&(log_sys->archive_lock));
  rw_lock_s_unlock(&(log_sys->archive_lock));

  mutex_enter(&(log_sys->mutex));

  /* Close all archived log files, incrementing the file count by 2,
  if appropriate */

  log_archive_close_groups(TRUE);

  mutex_exit(&(log_sys->mutex));

  /* Make a checkpoint, so that if recovery is needed, the file numbers
  of new archived log files will start from the right value */

  success = FALSE;

  while (!success)
  {
    success = log_checkpoint(TRUE, TRUE);
  }

  mutex_enter(&(log_sys->mutex));

  log_sys->archiving_state = LOG_ARCH_STOPPED;

  mutex_exit(&(log_sys->mutex));

  return (DB_SUCCESS);
}

/********************************************************************
Starts again archiving which has been stopped. */

ulint log_archive_start(void)
/*===================*/
/* out: DB_SUCCESS or DB_ERROR */
{
  mutex_enter(&(log_sys->mutex));

  if (log_sys->archiving_state != LOG_ARCH_STOPPED)
  {
    mutex_exit(&(log_sys->mutex));

    return (DB_ERROR);
  }

  log_sys->archiving_state = LOG_ARCH_ON;

  os_event_set(log_sys->archiving_on);

  mutex_exit(&(log_sys->mutex));

  return (DB_SUCCESS);
}

/********************************************************************
Stop archiving the log so that a gap may occur in the archived log files. */

ulint log_archive_noarchivelog(void)
/*==========================*/
/* out: DB_SUCCESS or DB_ERROR */
{
loop:
  mutex_enter(&(log_sys->mutex));

  if (log_sys->archiving_state == LOG_ARCH_STOPPED || log_sys->archiving_state == LOG_ARCH_OFF)
  {
    log_sys->archiving_state = LOG_ARCH_OFF;

    os_event_set(log_sys->archiving_on);

    mutex_exit(&(log_sys->mutex));

    return (DB_SUCCESS);
  }

  mutex_exit(&(log_sys->mutex));

  log_archive_stop();

  os_thread_sleep(500000);

  goto loop;
}

/********************************************************************
Start archiving the log so that a gap may occur in the archived log files. */

ulint log_archive_archivelog(void)
/*========================*/
/* out: DB_SUCCESS or DB_ERROR */
{
  mutex_enter(&(log_sys->mutex));

  if (log_sys->archiving_state == LOG_ARCH_OFF)
  {
    log_sys->archiving_state = LOG_ARCH_ON;

    log_sys->archived_lsn = ut_dulint_align_down(log_sys->lsn, OS_FILE_LOG_BLOCK_SIZE);
    mutex_exit(&(log_sys->mutex));

    return (DB_SUCCESS);
  }

  mutex_exit(&(log_sys->mutex));

  return (DB_ERROR);
}

/********************************************************************
Tries to establish a big enough margin of free space in the log groups, such
that a new log entry can be catenated without an immediate need for
archiving. */
static void log_archive_margin(void)
/*====================*/
{
  log_t *log = log_sys;
  ulint age;
  ibool sync;
  ulint dummy;
loop:
  mutex_enter(&(log->mutex));

  if (log->archiving_state == LOG_ARCH_OFF)
  {
    mutex_exit(&(log->mutex));

    return;
  }

  age = ut_dulint_minus(log->lsn, log->archived_lsn);

  if (age > log->max_archived_lsn_age)
  {
    /* An archiving is urgent: we have to do synchronous i/o */

    sync = TRUE;
  }
  else if (age > log->max_archived_lsn_age_async)
  {
    /* An archiving is not urgent: we do asynchronous i/o */

    sync = FALSE;
  }
  else
  {
    /* No archiving required yet */

    mutex_exit(&(log->mutex));

    return;
  }

  mutex_exit(&(log->mutex));

  log_archive_do(sync, &dummy);

  if (sync == TRUE)
  {
    /* Check again that enough was written to the archive */

    goto loop;
  }
}
#endif /* UNIV_LOG_ARCHIVE */

/************************************************************************
Checks that there is enough free space in the log to start a new query step.
Flushes the log buffer or makes a new checkpoint if necessary. NOTE: this
function may only be called if the calling thread owns no synchronization
objects! */

void log_check_margins(void)
/*===================*/
{
loop:
  log_flush_margin();

  log_checkpoint_margin();

#ifdef UNIV_LOG_ARCHIVE
  log_archive_margin();
#endif /* UNIV_LOG_ARCHIVE */

  mutex_enter(&(log_sys->mutex));

  if (log_sys->check_flush_or_checkpoint)
  {
    mutex_exit(&(log_sys->mutex));

    goto loop;
  }

  mutex_exit(&(log_sys->mutex));
}

/********************************************************************
Makes a checkpoint at the latest lsn and writes it to first page of each
data file in the database, so that we know that the file spaces contain
all modifications up to that lsn. This can only be called at database
shutdown. This function also writes all log in log files to the log archive. */

void logs_empty_and_mark_files_at_shutdown(void)
/*=======================================*/
{
  dulint lsn;
  ulint arch_log_no;

  if (srv_print_verbose_log)
  {
    ut_print_timestamp(stderr);
    fprintf(stderr, "  InnoDB: Starting shutdown...\n");
  }
  /* Wait until the master thread and all other operations are idle: our
  algorithm only works if the server is idle at shutdown */

  srv_shutdown_state = SRV_SHUTDOWN_CLEANUP;
loop:
  os_thread_sleep(100000);

  mutex_enter(&kernel_mutex);

  /* Check that there are no longer transactions. We need this wait even
   for the 'very fast' shutdown, because the InnoDB layer may have
   committed or prepared transactions and we don't want to lose them. */

  if (trx_n_mysql_transactions > 0 || UT_LIST_GET_LEN(trx_sys->trx_list) > 0)
  {
    mutex_exit(&kernel_mutex);

    goto loop;
  }

  if (srv_fast_shutdown == 2)
  {
    /* In this fastest shutdown we do not flush the buffer pool:
    it is essentially a 'crash' of the InnoDB server.
    Make sure that the log is all flushed to disk, so that
    we can recover all committed transactions in a crash
    recovery.
    We must not write the lsn stamps to the data files, since at a
    startup InnoDB deduces from the stamps if the previous
    shutdown was clean. */

    log_buffer_flush_to_disk();
    return; /* We SKIP ALL THE REST !! */
  }

  /* Check that the master thread is suspended */

  if (srv_n_threads_active[SRV_MASTER] != 0)
  {
    mutex_exit(&kernel_mutex);

    goto loop;
  }

  mutex_exit(&kernel_mutex);

  mutex_enter(&(log_sys->mutex));

  if (
#ifdef UNIV_LOG_ARCHIVE
      log_sys->n_pending_archive_ios ||
#endif /* UNIV_LOG_ARCHIVE */
      log_sys->n_pending_checkpoint_writes || log_sys->n_pending_writes)
  {
    mutex_exit(&(log_sys->mutex));

    goto loop;
  }

  mutex_exit(&(log_sys->mutex));

  if (!buf_pool_check_no_pending_io())
  {
    goto loop;
  }

#ifdef UNIV_LOG_ARCHIVE
  log_archive_all();
#endif /* UNIV_LOG_ARCHIVE */

  log_make_checkpoint_at(ut_dulint_max, TRUE);

  mutex_enter(&(log_sys->mutex));

  lsn = log_sys->lsn;

  if ((ut_dulint_cmp(lsn, log_sys->last_checkpoint_lsn) != 0)
#ifdef UNIV_LOG_ARCHIVE
      || (srv_log_archive_on && ut_dulint_cmp(lsn, ut_dulint_add(log_sys->archived_lsn, LOG_BLOCK_HDR_SIZE)) != 0)
#endif /* UNIV_LOG_ARCHIVE */
  )
  {
    mutex_exit(&(log_sys->mutex));

    goto loop;
  }

  arch_log_no = 0;

#ifdef UNIV_LOG_ARCHIVE
  UT_LIST_GET_FIRST(log_sys->log_groups)->archived_file_no;

  if (0 == UT_LIST_GET_FIRST(log_sys->log_groups)->archived_offset)
  {
    arch_log_no--;
  }

  log_archive_close_groups(TRUE);
#endif /* UNIV_LOG_ARCHIVE */

  mutex_exit(&(log_sys->mutex));

  mutex_enter(&kernel_mutex);
  /* Check that the master thread has stayed suspended */
  if (srv_n_threads_active[SRV_MASTER] != 0)
  {
    fprintf(stderr, "InnoDB: Warning: the master thread woke up during shutdown\n");

    mutex_exit(&kernel_mutex);

    goto loop;
  }
  mutex_exit(&kernel_mutex);

  fil_flush_file_spaces(FIL_TABLESPACE);
  fil_flush_file_spaces(FIL_LOG);

  /* The call fil_write_flushed_lsn_to_data_files() will pass the buffer
  pool: therefore it is essential that the buffer pool has been
  completely flushed to disk! (We do not call fil_write... if the
  'very fast' shutdown is enabled.) */

  if (!buf_all_freed())
  {
    goto loop;
  }

  /* The lock timeout thread should now have exited */

  if (srv_lock_timeout_and_monitor_active)
  {
    goto loop;
  }

  /* We now let also the InnoDB error monitor thread to exit */

  srv_shutdown_state = SRV_SHUTDOWN_LAST_PHASE;

  if (srv_error_monitor_active)
  {
    goto loop;
  }

  /* Make some checks that the server really is quiet */
  ut_a(srv_n_threads_active[SRV_MASTER] == 0);
  ut_a(buf_all_freed());
  ut_a(0 == ut_dulint_cmp(lsn, log_sys->lsn));

  if (ut_dulint_cmp(lsn, srv_start_lsn) < 0)
  {
    fprintf(stderr,
            "InnoDB: Error: log sequence number at shutdown %lu %lu\n"
            "InnoDB: is lower than at startup %lu %lu!\n",
            (ulong)ut_dulint_get_high(lsn), (ulong)ut_dulint_get_low(lsn), (ulong)ut_dulint_get_high(srv_start_lsn),
            (ulong)ut_dulint_get_low(srv_start_lsn));
  }

  srv_shutdown_lsn = lsn;

  fil_write_flushed_lsn_to_data_files(lsn, arch_log_no);

  fil_flush_file_spaces(FIL_TABLESPACE);

  fil_close_all_files();

  /* Make some checks that the server really is quiet */
  ut_a(srv_n_threads_active[SRV_MASTER] == 0);
  ut_a(buf_all_freed());
  ut_a(0 == ut_dulint_cmp(lsn, log_sys->lsn));
}

/**********************************************************
Checks by parsing that the catenated log segment for a single mtr is
consistent. */

ibool log_check_log_recs(
    /*===============*/
    byte *buf,            /* in: pointer to the start of the log segment
                          in the log_sys->buf log buffer */
    ulint len,            /* in: segment length in bytes */
    dulint buf_start_lsn) /* in: buffer start lsn */
{
  dulint contiguous_lsn;
  dulint scanned_lsn;
  byte *start;
  byte *end;
  byte *buf1;
  byte *scan_buf;

#ifdef UNIV_SYNC_DEBUG
  ut_ad(mutex_own(&(log_sys->mutex)));
#endif /* UNIV_SYNC_DEBUG */

  if (len == 0)
  {
    return (TRUE);
  }

  start = ut_align_down(buf, OS_FILE_LOG_BLOCK_SIZE);
  end = ut_align(buf + len, OS_FILE_LOG_BLOCK_SIZE);

  buf1 = mem_alloc((end - start) + OS_FILE_LOG_BLOCK_SIZE);
  scan_buf = ut_align(buf1, OS_FILE_LOG_BLOCK_SIZE);

  ut_memcpy(scan_buf, start, end - start);

  recv_scan_log_recs(TRUE, (buf_pool->n_frames - recv_n_pool_free_frames) * UNIV_PAGE_SIZE, FALSE, scan_buf,
                     end - start, ut_dulint_align_down(buf_start_lsn, OS_FILE_LOG_BLOCK_SIZE), &contiguous_lsn,
                     &scanned_lsn);

  ut_a(ut_dulint_cmp(scanned_lsn, ut_dulint_add(buf_start_lsn, len)) == 0);
  ut_a(ut_dulint_cmp(recv_sys->recovered_lsn, scanned_lsn) == 0);

  mem_free(buf1);

  return (TRUE);
}

/**********************************************************
Peeks the current lsn. */

ibool log_peek_lsn(
    /*=========*/
    /* out: TRUE if success, FALSE if could not get the
    log system mutex */
    dulint *lsn) /* out: if returns TRUE, current lsn is here */
{
  if (0 == mutex_enter_nowait(&(log_sys->mutex), __FILE__, __LINE__))
  {
    *lsn = log_sys->lsn;

    mutex_exit(&(log_sys->mutex));

    return (TRUE);
  }

  return (FALSE);
}

/**********************************************************
Prints info of the log. */

void log_print(
    /*======*/
    FILE *file) /* in: file where to print */
{
  double time_elapsed;
  time_t current_time;

  mutex_enter(&(log_sys->mutex));

  fprintf(
      file,
      "Log sequence number %lu %lu\n"
      "Log flushed up to   %lu %lu\n"
      "Last checkpoint at  %lu %lu\n",
      (ulong)ut_dulint_get_high(log_sys->lsn), (ulong)ut_dulint_get_low(log_sys->lsn),
      (ulong)ut_dulint_get_high(log_sys->flushed_to_disk_lsn), (ulong)ut_dulint_get_low(log_sys->flushed_to_disk_lsn),
      (ulong)ut_dulint_get_high(log_sys->last_checkpoint_lsn), (ulong)ut_dulint_get_low(log_sys->last_checkpoint_lsn));

  current_time = time(NULL);

  time_elapsed = 0.001 + difftime(current_time, log_sys->last_printout_time);
  fprintf(file,
          "%lu pending log writes, %lu pending chkp writes\n"
          "%lu log i/o's done, %.2f log i/o's/second\n",
          (ulong)log_sys->n_pending_writes, (ulong)log_sys->n_pending_checkpoint_writes, (ulong)log_sys->n_log_ios,
          ((log_sys->n_log_ios - log_sys->n_log_ios_old) / time_elapsed));

  log_sys->n_log_ios_old = log_sys->n_log_ios;
  log_sys->last_printout_time = current_time;

  mutex_exit(&(log_sys->mutex));
}

/**************************************************************************
Refreshes the statistics used to print per-second averages. */

void log_refresh_stats(void)
/*===================*/
{
  log_sys->n_log_ios_old = log_sys->n_log_ios;
  log_sys->last_printout_time = time(NULL);
}
